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akin, hakki e.
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alrowaijeh, jamal s.
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arbogast, steven m.
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arledge, richard k.
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NASA and private launch providers have a need to understand and control ignition overpressure blast waves that are generated by a solid grain rocket during ignition. Research in accurate computational fluid dynamics prediction of the launch environment is underway. A clearer picture is emerging from empirical data which more precisely categorizes all the dissipative mechanisms present in droplet-shock interactions. In this dissertation, water droplets and their effects due to vaporization are...
Topic: Fluid dynamics.
Naval Postgraduate School
by Korkut, Murat
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The goal of this study is to investigate the nonlinear dynamics of two ships in close proximity towing. The sway and yaw dynamics of both the leading and the trailing ships were included in the formulation. Previous studies were restricted to a linear analysis, which can accurately predict the regions of stability and instability for the system. The mechanism of loss of stability can be assessed with a systematic nonlinear analysis. The analysis is based on Taylor series expansions of the...
Topics: Nonlinear theories, Dynamics, Marine towing, Directional stability, Nonlinear dynamics, Towing
There has been increased interest in the dynamic behavior of sand throughout scientific and engineering communities due, mainly, to its damaging mechanisms against armored military vehicles upon sudden acceleration from buried improvised explosive devices. NASA is also interested in the properties of sand as a stimulant for powdered planetary materials. This thesis focused on developing the experimental techniques to successfully measure its dynamic response to shock impacts. However, sand has...
Topics: Physics, Impact, Dynamics
This study incorporated two approaches to determine the thermal conductivity of nanocomposite material using numerical modeling and simulation. The first was to look at the nanocomposite material at the macro level using a continuum model. The second approach broke the problem down to the atomic level and addressed the inter-atomic reactions using the Molecular Dynamics model. The continuum model was used to determine the optimal placement and alignment of the nanoparticles within a...
Topics: Nanocomposites (Materials), Molecular dynamics
Naval Postgraduate School
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Open-water sediment disposal is used in many applications around the world, including land reclamation, dredging, and contaminated sediment isolation. Timely examples include the land reclamation campaign currently underway in Singapore and the Boston Harbor Navigation Improvement Project. Both of these projects required the precise dumping of millions of cubic meters of purchased sediment, in the former example, and dredged material (both clean and contaminated), in the latter example. This...
Topics: Particles, Navigation, Dynamics, Speed
Naval Postgraduate School
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Identifying the influence of eastern boundary current (EBC) dynamical processes on sound speed structure can provide better ocean models for acoustic predictions in littoral regions. This study will explore the effects of currents, wind and eddies on the sound speed structure of two different EBC models, the North Canary Current System (NCCS) and the Leeuwin Current System (LCS). These systems represent classical features of EBCs as well as regional anomalies. This study seeks to introduce...
Topics: Acoustic streaming, Dynamics
Determining bulk mechanical properties from microscopic forces has become important in the light of utilizing nano-scale systems. The molecular dynamics model was used to determine the modulus of elasticity and shear modulus of pure metallic micro lattice structures. Preliminary results indicate that the modulii of elasticity is determined to within 15% accuracy for 5 different metals of 500-atom structures when compared to the experiment values of bulk materials. Furthermore the elastic...
Topics: Molecular dynamics, Quantum theory, Elasticity
Naval Postgraduate School
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The problem of estimating frequencies of sinusoids buried in noise has been great interest in both military and civilian applications. In particular, in Control Systems with flexible appendages the sinusoidal vibrations can cause instabilities and degrade performance of the overall system. In this thesis the problem of identifying frequencies disturbances in flexible systems using advanced Digital Signal Processing techniques such as filter banks and Quadrature Mirror Filters is addressed. In a...
Topics: Electrical engineering, Space, Technology, Dynamics
The concept of a fan-wing aircraft configuration for the purpose of vertical takeoff and landing has drawn much attention. Recently, more investigations revealed that a cross-flow fan (CFF) was capable of providing the propulsion. Several characteristics of the off-design performance of a CFF were experimentally measured, but insufficient numerical predictions were obtained. In the present study, the commercial CFD software ANSYS CFX was employed to calculate the unsteady flow through a CFF...
Topics: Computational fluid dynamics, Mechanical engineering
A numerical study has been performed to investigate the feasibility of hydro-dynamically based detection of propagating submersibles. Of particular concern is the possibility of utilizing microstructure measurements as a means of wake identification. The simulations are based on the Massachusetts Institute of Technology General Circulation Model (MITgcm), which has been modified for wake analysis. The dissipation of a turbulent wake produced by a sphere uniformly propagating in a doubly...
Topics: fluid dynamics, submarine, wakes, turbulence
Naval Postgraduate School
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This thesis provides a MATLAB (copyright) code and graphical user interface (GUI) which rapidly estimates the bending frequencies of rotating beams from the knowledge of bending frequencies of nonrotating beams. The approach is based on the Rayleigh energy method developed by Yntema. The beams may be rotating or nonrotating, cantilever or hinged, uniform or with linear mass and stiffness distributions, with or without root offsets from the axis of rotation; or uniform with or without tip mass....
Topics: Rotors (Helicopters), Aerodynamics, Rotors, Dynamics
Naval Postgraduate School
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As part of an initial baseline survey of the inlet flow-field into a transonic compressor rotor, a five-hole probe was calibrated and used to determine the Mach number and inlet pitch angle distributions. The data for Mach number were compared to data obtained with a three-hole probe. A numerical investigation of the flow in the inlet ducting to the rotor was also initiated using the commercial code CFX marketed by ANSYS. Comparisons were also made between the numerical predictions and the...
Topics: Mechanical engineering, Computational fluid dynamics
Naval Postgraduate School
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As the United States Navy prepares to field a single engine jet, the F-35C Joint Strike Fighter, it is important that the causes of the .pop-stall. occurrence be understood. This problem arises as the jet engine ingests steam just prior to being released from the catapult. In examining this problem two Computational Fluid Dynamic (CFD) codes have been used by the Naval Postgraduate School to predict the performance of a transonic compressor rotor that is being tested with steam ingestion. Both...
Topics: Mechanical engineering, Computational fluid dynamics
Naval Postgraduate School
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Computer simulation is a valuable tool for the research of physics. These simulations can be especially valuable when there is experimental data available that can be used to validate the model. The main objective of this thesis is to determine whether a computer simulation model can accurately depict the experimentally determined fluid flow for a channel with a series of unique individual constrictions. The experimental data are derived from a scaled-up model of coronary blood flow with...
Topics: COMSOL, Stenosis, Fluid Dynamics, Hemodynamics
The inherent characteristics of a cross-flow fan allowing for easy thrust vectoring as well as potential airfoil boundary layer control make it an attractive propulsive means for a theoretical vertical takeoff and landing aircraft. However, to compete with current methods of aircraft propulsion, further performance improvements of the cross-flow fan are needed. A baseline model of a cross-flow fan geometry developed by Vought Systems in the 1970s was scaled from a 12- inch diameter rotor to a...
Topics: Cross-flow (Aerodynamics), Fluid dynamics
Naval Postgraduate School
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Control of a modern submarine is a multi-dimensional problem coupling initial stability, hydrodynamic and control system response. The loss of stability at moderate to high speeds is examined using a nonlinear Hopf bifurcation analysis. Complete linear state feedback is used for demonstration purposes for depth control at level attitude and for a fixed nominal speed. Control time constant, nominal and actual speeds, metacentric height, and stern to bow plane deflection ratio are used as the...
Topics: Submarine, Bifurcation, Nonlinear dynamics, Chaos
Naval Postgraduate School
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ry at simulated flight conditions, including supersonic cruising conditions. The spiral lines initiator demonstrated a lower total pressure loss with compared to the geometry with rings, and thus was the preferred initiator configuraiton. Experimental values for the turbulence were found to be significantly lower than the computed values at similar conditions when using the k-e model. Finally, successful ignitions of the JP-10/Air initiator at frequencies of up to 20 Hz were experimentally...
Topics: Computational fluid dynamics, Mechanical engineering
Naval Postgraduate School
by Harrell, Anthony F.
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Polymers have been widely used in various engineering applications. For more than a quarter century, the materials have been utilized intensively for the binding materials for composites. The material properties of the binding materials called matrix materials play an important role for the composite material behaviors. As a result, the objective of this study was to understand the mechanical properties of polymers. In particular, the goal was to develop insights as to how a molecular level...
Topics: Embedded Atom Method, Lennard Jones Potential, Metallic Potential, Molecular Dynamics, Molecular...
This thesis reports on the evolved design, test, and integration of a robotic manipulator consisting of multiple modular links, which enable the reconfiguration of the manipulator system for differing mission requirements without constructing unique hardware for each experimental campaign. The evolved design replaced custom components with commercial components to improve performance, standardize hardware, and reduce assembly time. Additional links were constructed and assembled into a...
Topics: spacecraft, robotics, kinematics, dynamics, multi-body mechanics
The flow around second-generation controlled diffusion blades in cascade at stall was examined experimentally through the use of a two-component laser-Doppler velocimeter (LDV). The experimental results were compared with computational fluid dynamics predictions in order to provide information that will allow for more exact design of advanced blades. Midspan blade surface pressure data were also collected over a range of Reynolds numbersbased on chord of 270,000 to 720,000. Pressure...
Topics: Mechanical engineering, Fluid dynamics, Diffusion, Doppler effect
Naval Postgraduate School
by New, David M.; Estrada, Luis E.
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Stenoses (blockages) in coronary arteries cause heart attack, which the Centers for Disease Control and Prevention ranks as the leading cause of death among American adults. We have performed computer simulations in order to understand the flow patterns due to stenoses with and without a guidewire used for interventional procedures (e.g., stent deployment). Building off previous models that have been partially validated with experimental data, this thesis continues to develop the models in...
Topics: COMSOL, Stenosis, Fluid Dynamics, Hemodynamics, Slip
Naval Postgraduate School
by Bradford, Ellen M.
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The inverted pendulum, a popular problem of study, is presented in many textbooks as a nonminimum phase system. The majority of control algorithms for this problem include linearizing the system about a fixed operating point. In this thesis, a nonlinear form of control is considered. A model for the rotary inverted pendulum system was derived and validated by comparing simulations using the derived equations to experimental data. The system parameters were tuned until the simulation and...
Topics: inverted pendulum, nonlinear feedback, zero dynamics
The ability to enhance detonation wave transmission at a diffraction plane through various shock reflection/focusing conditions was evaluated numerically. The geometry dimensions were generally representative of the condition existing in a valve-less pulse detonation engine developed by the Naval Postgraduate School and consisted of a small cylindrical \"initiator\" combustor, which transmitted a shock wave to a larger diameter combustor. The wall cross section of the larger combustor...
Topics: Combustion chambers, Fluid dynamics, Detonation waves
Naval Postgraduate School
by Jacinto, Arturo, II
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This thesis implements the development of a Robotic Manipulation Laboratory to explore learning opportunities for various student experiments including the initial selection, startup and development of the Robotic arm and glove controller. The Robotic Manipulation Laboratory consists of a 6 Degree of Freedom robotic arm and a resistive glove controller that allows students to achieve hands-on understanding of the physics required to fabricate and maneuver a robotic arm. The Kinova JACO robotic...
Topics: robotic arm, glove controller, dynamics, DH parameters
Naval Postgraduate School
by Coelho, Emanuel Ferreira
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Coastal currents and water column stratification frequently are determined by local phenomena that interact to produce complex dynamics. A process study was designed to assess the role of tides over a coastal shelf break as a local source of internal waves spatially-inhomogeneous, baroclinic residual currents, and internal mixing. The temporal evolution of three dimensional stratification and currents were characterized within a 4km x 4km box close to the mouth of Monterey Canyon, California....
Topic: Internal Tide, Tidal mixing, internal waves, coastal dynamics, nonlinear internal wave propagation,...
Naval Postgraduate School
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This study used the Computational Fluid Dynamics code, ANSYS-CFX to predict the static aerodynamic characteristics of a canard-wing missile configuration with a hemispherical nose, triangular wedge canards and fixed trapezoidal wings. The study was conducted for Mach numbers of 0.2, 0.8 and 1.2. The results were compared against experimental data from actual wind tunnel tests and data from a semi-empirical method, AP09. The ANSYS-CFX results showed good agreement for CN, CM, and CL but less...
Topics: Computational fluid dynamics., ANSYS, CFX, canard, Computational Fluid Dynamics, missile, AP09
Molecular dynamics simulations were performed to determine the Young's modulus of the single-walled carbon nanotubes (SWNT) and bamboo structural carbon nanoutbes (BSNT) models generated from the basic structure characteristics of graphite. The empirical Tersoff-Brenner potential and freestanding thermal vibration methods proposed by Krishnan et al. were used to determine the interatomic forces and displacements of carbon atoms at room temperature 300 K. The calculated average Young's modulus...
Topics: Molecular dynamics, Ionic equilibrium, Nanotubes, Nanotechnology
Naval Postgraduate School
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Pulse detonation combustion offers thermodynamic advantages to the next generation of combustion systems. The thermodynamic efficiency is substantially improved over constant-pressure combustion systems by utilizing detonation-based combustion that occurs typically between 40 and 60 pulses per second. An existing four-inlet combustor was modified to a single-inlet arm design for integration with a rotary-valve concept. This paper discusses the design process of the single-inlet combustor so...
Topics: Mechanical engineering, Combustion chambers, Computational fluid dynamics
Naval Postgraduate School
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There are 80 million light trucks on the road today with suboptimal aerodynamic forms. Previous research has found that several miles per gallon can be saved by specifically tailoring truck bodies for reduced aerodynamic drag. Even greater savings can be obtained if the shape of the trucks is numerically optimized. This could reduce fuel consumption in the United States by billions of gallons per year. The purpose of this research is to develop and quantify optimal light truck canopy designs...
Topics: Energy consumption, United States, Fluid dynamics
Composite materials are seeing increased use in structural applications because of their various benefits. When composite structures are employed in a water environment, their dynamic responses are greatly affected by the fluid medium. Water density is comparable to many composite materials and the effects of fluid-structure interaction on dynamic behaviors of composite structures are significant. The effects of fluid-structure interaction include changes of frequency, magnitude, energy...
Topics: Fluid-structure interaction, Structural dynamics, Carbon composites
An existing freejet facility was upgraded and its range of operation extended into the high subsonic regime for operation as a test rig for the development of a combined-cycle, turbo-ramjet engine. A combustor was designed, developed, and tested as the afterburner for the turbo-ramjet engine. At subsonic speeds with the afterburner running, an increase in thrust of 40% was measured over the baseline turbojet running at 80% spool speed. A Computational Fluid Dynamics model of the flow through...
Topics: Airplanes, Ramjet engines, Combustion, Fluid dynamics
Naval Postgraduate School
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This thesis presents a Computation Fluid Dynamics (CFD) analysis of the aerodynamic performance of circular and elliptical leading edges of compressor blades, with a range of leading-edge droop angles. Specifically, simulations were conducted, with a free stream Mach number of 0.65 to quantify the change in pressure distributions and boundary layer momentum thickness in the leading edge region for a range of incidences on a flat plate with various leading-edge ellipticity ratios, ranging from...
Topics: Leading edges (Aerodynamics), Blades, Compressors, Fluid dynamics
Naval Postgraduate School
by Kutrieb, Joshua M.
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Interest in accurate detection and targeting of aggressor missiles has received considerable interest with the national priority of developing a missile defense system. Understanding the thermal signatures of the exhaust plumes of such missiles is key to accomplishing that mission. Before signature models can be precisely developed for specific rockets, the radiation of the molecular or combustion species within those plumes must be accurately predicted. A combination translation / rotation...
Topics: Rocket engines, Exhaust emissions, Plumes (Fluid dynamics)
Naval Postgraduate School
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This study forms part of a larger study to develop a MEMS scale turbomachinery based vacuum pump. This would allow very high vacuum to be drawn for handheld mass spectroscopy. This thesis concentrates on the roughing portion of the turbo pump where flow can still be treated as a continuum but the no slip boundary condition is not accurate. The first portion of this thesis investigates flow at Knudsen numbers ranging from 0.001 to 0.1. By using a first order analysis, the wall shear stress can...
Topics: MEMS Turbomachinery, Computational Fluid Dynamics, Vacuum Pumps
Naval Postgraduate School
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Incorporating an azimuth/podded propulsion into an ice-capable ship brings concern in the propellers durability and lifecycle. An ice impact model was constructed to have a better understanding of collisions occurring between ice and azimuth/podded propeller for ice operation ships. A typical propeller profile was created using MATLAB and modeled in SolidWorks using realistic material properties. The ANSYS Explicit Dynamics solver was used to simulate the ice-propeller impact. By conducting a...
Topics: Ice impact, azimuth propeller, explicit dynamics
Naval Postgraduate School
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The strain pattern analysis (SPA) method is applied to estimate rotor blade torsional deflections. The SPA technique requires calculated mode shapes for the tested rotor blade and strain measurements from the rotor's wind tunnel or flight test. The Holzer method is developed to calculate the required mode shapes from rotor blade stiffness and mass properties and the torsional equation of motion. The Holzer method is tested with numerous theoretical and experimental cases and is proven accurate....
Topics: Rotors (Helicopters), Rotor Wing Structural Dynamics, Torsional Deflection, Rotor Blade...
Autonomous aerial systems have started to gain much traction in the military intelligence, surveillance and reconnaissance domain. The remotely piloted systems, such as the Predator, are already successful unmanned systems; the next step forward is to use autonomous systems to overcome high manning requirements. These systems are scalable and serve as excellent force multipliers, but there are other technological issues to overcome to qualify an autonomous aerial system, such as navigation and...
Topics: autonomous system, quadrotors, direct method, inverse dynamics, virtual domain
Naval Postgraduate School
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This thesis investigates the development and implementation of optimal slew trajectories for positioning a spacecraft antenna. Conventional maneuvers are developed by considering each gimbal independently. Consequently, maneuver design is simple, but may be highly sub-optimal and cause significant torques to be imposed on the spacecraft body. This work explores the impact of implementing optimal slew paths that best utilize system dynamics with the objective of increasing available customer...
Topics: Optimal Slew Maneuvers, Spacecraft, Antenna, Communications Satellite, Multibody Dynamics
Astrobee is a robot designed by Intelligent Robotics Group at NASA Ames Research Center to operate inside of the International Space Station (ISS). The robot has a manipulator that is made up of various mechanical, electronic, and control systems. The designed purpose of the manipulator is to perch Astrobee in an effort to minimize power consumption. The study of grasping dynamics and hopping will lead to more efficient maneuvers that would not require propellant. Can the current Astrobee...
Topics: spacecraft, robotics, dynamics, multi-body mechanics, manipulators, and mechatronics
Naval Postgraduate School
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The Department of the Navy (DON) has prioritized the establishment of a robust renewable energy platform for its installations. Solar energy has emerged in a way that has provided viable alternatives. The use of solar energy, however, poses a problem of maintaining continuity of power during hours when sunlight is not available. The development of Thermal Energy Storage (TES), while addressing this problem, introduces complexities that can reduce overall plant efficiency. This research aims to...
Topics: thermal energy storage, thermodynamics, heat transfer, fluid dynamics
Naval Postgraduate School
by Fleming, Andrew
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This thesis considers the problem of time-optimal spacecraft slew maneuvers. Since the work of Bilimoria and Wie it has been known that the time-optimal reorientation of a symmetric rigid body was not the eigenaxis maneuver once thought to be correct. Here, this concept is extended to axisymmetric and asymmetric rigid body reorientations with idealized independent torque generating devices. The premise that the time-optimal maneuver is not, in general, an eigenaxis maneuver, is shown to hold...
Topics: Space vehicles, Control systems, Feedback control systems, Mathematical models, Dynamics
Operational experience indicates that steam escaping from carrier catapults has the potential to induce stall or surge in the compressors of jet aircraft during takeoff. As the carrier fleet ages and the Navy transitions to the single engine F-35C variant of the Joint Strike Fighter, further investigation of steaminduced surge phenomena is necessary to avert undue risks to pilots and to obviate stall related damage to Navy aircraft. This study investigated the effects of both throttle-induced...
Topics: Airplanes, Jet propulsion, Aircraft gas-turbines, Compressors, Fluid dynamics
Naval Postgraduate School
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An existing turbo-ramjet engine was modified in order to increase the produced thrust and sustain combustion at increased freejet Mach numbers. The engine's afterburner fuel system was redesigned to improve the vaporization and atomization of the fuel. The engine performed satisfactorily at speeds up to Mach 0.3, producing 100% more thrust over the baseline turbojet. The data acquisition system of the turbo-ramjet engine's performance measurement in a freejet facility was also updated. Various...
Topics: Airplanes, Ramjet engines, Combustion, Motors, Thrust, Fluid dynamics, Jets
Naval Postgraduate School
by Janvier, George
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This research involves the development of an adaptive control law for a space based two-link robotic manipulator. Non-adaptive controllers are first obtained utilizing feedback linearization techniques. A direct adaptive controller is then developed throu
Topics: adaptive control, robotic manipulators, spacecraft attitude dynamics and control
Naval Postgraduate School
by Claes, Dennis C.
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A two layer ocean mixed layer model is used to study the relationship between onset of freezing and mixed layer depth, wind forcing, surface buoyancy flux, and temperature and salinity changes between the two layers. Universal non- dimensional parameters for stability and surface forcing are derived and related to the maximum freezing rate. Analytic solutions to the model are found in terms of the universal parameters and the model turbulent mixing tuning constants. Sensitivity studies show the...
Topics: Dynamics, Temperature., Oceanography, sea ice, mixed layer modeling, freezing
Recently, most large corporations, including the Department of Defense and the Department of the Navy have seen a dramatic proliferation of incompatible databases and their associated database management systems. Sooner or later, these organizations discover the need to integrate the data in these incompatible databases. One solution to this problem is the use of mark-up languages like Abstract Syntax Notation One (ASN.1) as a standard format for representing these databases and output reports...
Topics: Ocean currents Pacific Ocean, Eddies, Fluid dynamics, Hydrography, NA
Topics: Space shuttle, CFD, Canard, Hypersonic aerodynamics, Computational fluid dynamics
Semiconductors continue to shrink in size and are now nearing the performance limits of some traditional materials. Silicon Dioxide, which has been used extensively as a gate insulator in MOSFETs, is one such material and so research is focusing on finding a suitable replacement with a high dielectric constant. Oxides of Lanthanum and Zirconium have been identified as possible successors, but these compounds have not been well studied. This thesis is the first step in an attempt to learn more...
Topics: Semiconductors, Molecular dynamics, Computer simulation, Thermal conductivity, Niobium-zirconium...
Naval Postgraduate School
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Flow around polished second-generation controlled-diffusion blades in cascade set at their design inlet flow angle was investigated at various Reynolds numbers using static pressure measurements, five-hole probe surveys, twocomponent laser Doppler velocimetry (LDV), computational fluid dynamics and flow visualization. A suction-side separation bubble formed at Reynolds number, based on chord length, of 203,000 and collapsed by a Reynolds number of 393,000. Five-hole probe surveys characterized...
Topics: Mechanical engineering, Diffusion, Control, Pressure, Measurement, Computational fluid dynamics
Naval Postgraduate School
by Carroll, John B.
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The unsteady flow phenomena resulting from the interaction of wakes and vortices with the free surface are of particular importance in naval hydrodynamics. Ship and submarine wakes produce a three-dimensional complex signature, comprised of a narrow dark band bordered by two bright lines in synthetic-aperture-radar (SAR) images. The dark band signifies the suppression of waves at the Bragg frequency as a consequence of the interaction between the free surface and the imposed vorticity. In the...
Topics: Surface disturbances, Scars, Striations, Trailing votices, Vortex dynamics
A full three dimensional computational study was carried out using a finite-volume based solver for analyzing the performance of pin-fin based micro/meso scale heat exchangers with air as the working fluid. A staggered arrangement of cylindrical pin fins in rectangular channel geometry was used. Various configurations were considered consistent with a parallel experimental study being conducted based on a micro-wind tunnel setup. The pin/channel height used was 0.4 mm, and the pin diameters...
Topics: Mechanical engineering, Computational fluid dynamics, Laminar flow, Reynolds number
Naval Postgraduate School
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The JACO six degree of freedom robotic arm and associated software is characterized for use by students in a Robotic Manipulation Laboratory. The lab was implemented to help students understand tele-operation techniques with a sophisticated Kinova JACO robotic arm. The purpose of the research was to follow up on Jacinto’s work and expose students to forward kinematics via Denavit-Hartenberg (DH) parameters for robotic arm manipulation in a lab environment for various experiments. Jacinto...
Topics: robotic arm, lagrangian dynamics, kinematics, inverse kinematics, DH parameters
Naval Postgraduate School
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The objective of this work is the investigation of vortical flows at high angles of attack using numerical techniques. The first step for a successful application of a numerical technique, such as fimite difference or finite volume, is the generation of a computational mesh which can capture adequately and accurately the important physics of the flow. Therefore, the first part of this work deals with the grid generation over a double-delta wing and the second part deals with the visualization...
Topics: Computational fluid dynamics., Word processing, script, GML, text processing
Naval Postgraduate School
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Langmuir circulations in a coastal environment at an inner shelf site with strong tidal forcing were examined using a 4-month observation of high-resolution velocity profiles during the ONR-sponsored CBLAST-Low air-sea interaction experiment. Because of their potential contributions to mixing processes in the surface boundary layer, Langmuir circulations are important for naval operations such as ASW, MCM and Amphibious operations in littoral waters. A detection algorithm for upwelling /...
Topics: Turbulence, Fluid dynamics, Boundary layer, Boundary layer (Meteorology), Tidal currents
Naval Postgraduate School
by Kiel, David H.
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The dynamics of the Free Electron Laser are governed by Maxwell's equations which causes many highly nonlinear regimes to exist in Free Electron Laser Physics. This thesis will examine two such areas and develop simple models to describe the highly dynamic and rich behavior two of these regimes. In the strong-field, high current regime, the Free Electron Laser driving current can be modeled by a single macroparticle representing the trapped electrons. When the trapped electrons act collectively...
Topics: Mathematical models, Dynamics, Electrons, Computers., FEL, Macroparticle, Oscillator
Naval Postgraduate School
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In view of the local, regional and global security trends over the past decade, the threats of disaster to the populace inhabiting urbanized areas are real and there is a need for increased vigilance. There can be multiple causes for urban disaster natural disasters, terrorist attack and urban warfare are all viable. This thesis focused on the event in which an urban search and rescue operation is required due to the aftermath of a terrorist activity. Systems engineering techniques were...
Topics: Quadrotor, UAV, Direct method, Urban environment, Urban Search and Rescue, Trajectory Optimization,...
Steam leakage from an aircraft carrier catapult is sometimes ingested into the aircraft engines upon launch which may induce compressor stall. Investigation of this phenomenon is of particular interest to the Navy with its new F35C, the aircraft carrier variant of the joint strike fighter. The single engine configuration of the F-35C makes this aircraft particularly vunerable to steam-induced stall. The present study examined both throttle-induced stall and steam-induced stall in a compressor...
Topics: Turbulence, Airplanes, Motors, Aircraft carriers, Pressure transducers, Computational fluid...
Naval Postgraduate School
by Lentsoane, Nape D.
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Metals have a very high energy density compared to explosives, but typically release this energy slowly via diffusion-limited combustion. There is recent interest in using molecular-scale metalloid clusters as a way to achieve very rapid rates of metal combustion. These clusters contain a mixture of low-valence metals as well as organic ligands. Here we investigate a prototypical aluminum metalloid cluster to determine system stability if the organic ligand contains significant amounts of...
Topics: density functional theory, molecular dynamics, binding energy, siesta code, density of states,...
During an underwater explosion (UNDEX) event, a cavitation zone is created which alters the shockwave propagation parameters through this region. A cavitation zone is generally comprised of air bubbles whose material properties closely resemble water vapor. Multiple scenarios were created using these properties to simulate the presence of bubble regions during an UNDEX event. Initial simulations involved large rectangular bubble regions which reduced the pressure from the initial shockwave,...
Topics: UNDEX, underwater explosion, shockwave, shock-induced bubble collapse, numerical analysis, DYSMAS...
This thesis is focused on the development of a six degrees of freedom (6DOF) simulation model of a commercial-off-the-shelf quadrotor. The dynamics of the quadrotor and its control strategy are described. The Geometric Dilution of Precision (GDOP) of the Autonomous Systems Engineering and Integration Laboratory (ASEIL) laboratory used in conducting the experiments is also analyzed. Simulation results are then verified with actual flight data. A direct method of calculus of variations is...
Topics: Quadrotor, Qball, 6DOF Model, PID, Direct Methods, Trajectory, Optimization, Inverse Dynamics,...
Sea ice area and thickness have been on the decline in the Arctic over the past several decades. Understanding the role of ice motion, deformation, and export is important to determining if the Arctic will continue toward seasonal ice coverage or if natural variability is capable of reversing this trend. We have analyzed sea ice model output and satellite data to advance the understanding of potentially critical physical processes and feedbacks in the region. In particular, comparisons of RGPS...
Topics: Arctic Ocean, Sea Ice Variability, Coupled Ice-Ocean Model, Sea Ice Dynamics, Sea Ice Thickness...
Naval Postgraduate School
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This study determined the optimum blade stagger angle for a cross-flow fan rotor and evaluated the performance of a 3D printed rotor. Using ANSYS-CFX and SolidWorks, the cross-flow fan was modeled computationally and tested at 8,000 rpm. A parametric study determined optimum blade stagger angle using thrust, power, and thrust-to-power ratio as desired output variables. A MarkForged Mark One 3D printer was used to print components of a carbon-fiber composite cross-flow fan rotor. These pieces...
Topics: cross-flow fan, vertical take-off and landing, 3D printing, computational fluid dynamics, VTOL, CFD
Rotating detonation engines (RDEs) have the potential to further increase the performance of air-breathing propulsion devices and are currently being explored as an option for missions with wide altitude and flight Mach number ranges. Aerospike nozzles lend themselves well to this type of application because they possess altitude-compensating characteristics. However, the effects of the unsteady nozzle inlet dynamics associated with RDEs on aerospike nozzle performance have not been fully...
Topics: rotating detonation engine, continuous detonation engine, pressure gain combustion, aerospike...
Naval Postgraduate School
by Silverberg, Jon P.
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Classically, fluid dynamics have been dealt with analytically because of the lack of numerical resources (Yeung, 1982). With the development of computational ability, many formulations have been developed which typically use the traditional Navier-Stokes equations along with an Eulerian grid. Today, there exists the possibility of using a moving grid (Lagrangian) along with a meshless discretization. The first issue in meshless fluid dynamics is the equations of motion. There are currently two...
Topics: Fluid dynamics, Lagrangian functions, Equations of motion, Boundary value problems, Polynomials,...
The Department of Defense lacks case studies that investigate and detail the innovation and adoption of information technology systems. This qualitative study develops a case study to explore the factors that contributed to the United States Marine Corps’ innovation and adoption of Ripper Academy, a video-streaming platform that allows Marines to create, share, and view user-generated video content. This research addresses the research question: How can the United States Marine Corps...
Topics: information technology, information technology system, IT, innovation, adoption, change management,...
Naval Postgraduate School
by Jurewicz, Thomas A.
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The NPS Autonomous Underwater Vehicle Simulator is a joint project between the Naval Postgraduate School's Mechanical Engineering and Computer Science Departments. In order to test mission planning and execution software, an accurate vehicle dynamic model is required. Using dynamics based upon the Navy's Swimmer Delivery Vehicle (SDV), there is a need to continually update the hydrodynamic coefficients based upon actual vehicle-in-water testing. The NPS AUV Dynamic Simulator contains a full set...
Topics: Computer science, Submersibles, Hydrodynamics, Computer programs., Graphics, Dynamics, Real Time,...
Naval Postgraduate School
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This thesis is centered upon an optimal trajectory generation algorithm that allows real-time control for cooperation of multiple quadrotor vehicles for intelligence, surveillance, and reconnaissance missions with minimal user input. The algorithm is designed for an indoor environment where global positioning system data is unavailable or unreliable, forcing the vehicles to obtain position data using other sensors. This thesis specifies the lab setup and well as the control approach used. Data...
Topics: Quadrotor, Cooperation, Quanser, LQR, Direct Methods, Trajectory Generation, Trajectory Following,...
which is similar to the Baseline but with a hierarchical structure. All models are tested under both baseline and high counterterrorist conditions. This thesis examines how different contingency factors affect the preparation and execution of a terrorist bombing attack and provides recommendations to inform counterterrorist agencies.
Topics: Terrorists, Madrid Train Bombings, Madrid, Spain, 2004, Terrorism, Spain, Madrid, Social aspects,...
Naval Postgraduate School
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The presence of an island is known to affect the marine environment in multiple ways depending on the size, shape, and particularly the topography of the island. The dominant effect is seen in the atmospheric boundary layer through the significant change in surface roughness and land surface heating, while steep topography on a small island may affect large scale systems such as tropical cyclones. In this study, we investigate the role of a small remote coral atoll, Diego Garcia, in the Indian...
Topics: Madden-Julian Oscillation (MJO), Dynamics of the Madden-Julian Oscillation (DYNAMO), Dropsonde
Naval Postgraduate School
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An investigation of the interaction of two-counter-rotating vortices with a free surface has been undertaken. Experiments were carried out in two water basins and in a long towing tank through the use of measurements, flow visualization, and an infrared camera. The results have shown that all types of vortex pairs over a wide range of Froude Numbers give rise to three-dimensional surface disturbances, known as scars and striations. The striations are a consequence of the short wavelength...
Topics: Dissertations, Academic, Scars., Surface disturbances, Scars, Striations, Trailing Vortices, Vortex...
Naval Postgraduate School
by Taylor, Katharin C.
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This thesis is part of a larger project that will demonstrate the feasibility of powering a commercially sized 7.5-ton cooling system. Excess cooling will be stored thermally using ice. This system has the potential to be used in military bases to reduce energy costs and fossil fuel consumption. A scaled down version would be suitable for data centers and forward operating bases where the transport of fuel can be costly and dangerous. The system will be built and operated at the Turbopropulsion...
Topics: Commercial cooling system, vertical axis wind turbines, horizontal axis wind turbines,...
Naval Postgraduate School
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The purpose of this thesis was to design and demonstrate the effectiveness of a new style of heat exchanger for waste heat recovery. The new design sought to optimize heat recovery from a gas turbine engine exhaust as well as assist with flow turning through a bend in the exhaust duct in order to minimize back-pressure increases. The analysis of the design was based around the use of the Allison 250 gas turbine engine. An analysis of the engine was performed to determine baseline operating...
Topics: waste heat recovery, turning vanes, heat transfer, computational fluid dynamics, back-pressure
Naval Postgraduate School
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This thesis investigates the implementation of optimal control solutions for positioning spacecraft antenna using conventional techniques. Conventional maneuvers consider each axis independently and may include artificial limits that reduce the efficiency of the system. These methods allow simple, but generally suboptimal, maneuver design. Multi-body dynamic systems do, however, exhibit coupling effects that can be advantageous for enhancing motion planning. Including coupling effects in the...
Topics: Optimal Slew Maneuvers, Spacecraft, Antenna, Communications Satellite, Multi-body Dynamics, Dynamic...
Naval Postgraduate School
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This research evaluates the production of three dimensional (3D) clouds for geospatial viewing programs such as Google Earth, NASA World Wind, and X3D Earth. This thesis took advantage of iso-standard X3D graphics and X3D Edit in conjunction with manually produced image textures to represent 3D clouds. While a 3D geospatial viewing might never completely characterize the current state of the atmosphere, a sufficiently realistic virtual 3D rendering can be created to present current sky coverage...
Topics: Clouds, Dynamics, Three-dimensional display systems, X3D (Standard), XML (Document markup...
Naval Postgraduate School
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Military operations other than war (MOOTW) make up a large percentage of total military operations. Some common MOOTW operations are peacekeeping (PKO) and humanitarian assistance, and disaster relief (HADR). System dynamics (SD) uses a top-down approach that models high-level system behavior as compared to the use of agent-based modeling (ABM), which uses a bottom-up approach to generate system-level behavior through emergent behavior. In this work, SD and ABM were applied to model a food...
Topics: Modeling and Simulation, System Dynamics, Agent-Based Modeling, Discrete Event Simulation,...
Naval Postgraduate School
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Military conflicts are shifting from jungles and deserts to cities. This is because terrorists, insurgents, and guerillas find these areas provide a rich target environment and good hideouts. With the use of UAVs, urban threats can be tracked and targeted effectively. However, in an urban environment where there is little or no GPS signals and many obstacles, navigation of UAVs is a major challenge. Multiple UAVs can be employed to share sensor information to counter these challenges and to...
Topics: Quadrotor, UAVs, Interoperability, Direct method, Urban environment, Trajectory Following,...
Naval Postgraduate School
by Alrowaijeh, Jamal S.
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Multiscale mathematical modeling of flows containing particles is conducted in this study using computational fluid dynamics and molecular dynamics. The first study considered continuous media interaction of macro-scale fluid and micro-scale solid particles using computational fluid dynamics and rigid particle dynamics. This study investigates the potential enhancement of heat transfer properties of particulate fluid as well as the effect of injected particles on fluid profiles, and pressure on...
Topics: Liquids, Mathematical models, Data processing, Molecular dynamics, Computer simulation, Solids,...
Marine Corps commanders have inadequate tools for energy awareness on the battlefield. The purpose of this study is to explore how vehicle telematics could impact operational reach through improving awareness of fuel stocks from hours to near-real time. The research uses an exploratory sequential mixed methods design to establish how current practices may change with the introduction of telematics. The first-phase qualitative findings suggest that the tactical fuel supply chain is inherently...
Topics: Systems thinking, systems dynamics, feedback loops, supply chain management, data acquisition...
The Marine Corps Intelligence, Surveillance, and Reconnaissance Enterprise (MCISR-E) faces ever-increasing complexity in the conduct of expeditionary operations. This research seeks to explore computer-supported collaborative work of the MCISR-E. Properties of networks and complexity are explored through a systems thinking perspective on collective intelligence. Online social networking information technology is examined for demonstration of emergent knowledge creation for sensemaking in the...
Topics: Marine Corps, ISR, MCISR-E, Intelligence, Crowdsourcing, Collaboration, Adaptation, Technology,...
Naval Postgraduate School
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International arms sales are a useful tool in executing a country’s economic and foreign policy strategy. As such, investigating the drivers behind these exports discloses a state’s priorities. Since Vladimir Putin came to power, Russian arms sales have steadily increased in several geographic areas while Russo-American relations have gradually deteriorated. Therefore, as Putin seeks to foster global multi-polarity in order to challenge the American-dominated geopolitical world order, how...
Topics: arms sales, Russian foreign policy, Russian strategic goals, Russian military industrial complex,...
The Regional Arctic System Model (RASM) is used to investigate the process and frequency of extreme sea ice shear deformation events resulting in pycnocline upwelling due to Ekman pumping as described in McPhee et al. (2005). RASM is a fully coupled land, atmosphere, sea ice, and ocean model with high spatial and temporal resolution. Time series analysis of the upper ocean temperature structure, basal melt rate, total deformation rate, and ice-ocean stress curl yield the identification of...
Topics: Arctic Ocean, Sea Ice, RASM, Coupled Ice-Ocean Model, Sea Ice Dynamics, Sea Ice Thickness...
Naval Postgraduate School
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The Monterey Bay sea breeze varies because of the influence of features such as inversions, clouds, synopticscale flow, and topography. The sea breeze is important because it impacts fire weather, air pollution, agriculture, and aviation operations, among other things. Analyses are conducted using a multi-quadric based program, which incorporates aircraft data, surface observations, and profiler data, to investigate the Monterey Bay sea breeze during 01-31 August 2003. Factors including...
Topics: Sea breeze, California, Monterey Bay, Temperature inversions, Clouds, Dynamics, Synoptic-Scale...
This research investigates the capability of computational fluid dynamics to accurately model the performance of a vertically oscillating wave-generating wedge and resultant wave-induced loads on a submerged object in a tow tank. Specifically, the wave height, wave frequency, and unsteady forces on a submerged body were determined from numerous simulations and compared to experimentally measured data from nearly identical conditions as the simulations. Time histories of the water surface...
Topics: numerical wave generation, wedge-shaped wave maker, computational fluid dynamics, CFD, loads on...
Naval Postgraduate School
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This research will be used to evaluate the feasibility of robotically, or remotecontrolled firefighting nozzles aboard air-capable ships. A numerical model was constructed and analyzed, using the program CFD-ACE, of a fire hose stream being deflected by the influence of a crosswind, tailwind, or headwind. The model is intended to predict the reach of the fire hose stream, indicate the distribution pattern, and estimate the volume of fire fighting agent available at the end of the stream....
Topics: Fire extinction, Aircraft carriers, Flight decks, Fluid dynamics, Approximation methods, Equipment...
Naval Postgraduate School
by Jung, Sunghoon
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This study presented a computational technique to model and simulate atomistic behavior of materials under static loads. Interatomic potential energy was used to maintain equilibrium among atoms under static loads and constraints. In addition, the atomistic model was coupled with the finite element analysis model so that more flexible loads and constraints could be applied to the atomistic model. A multi-scale technique was also presented for some single wall nanotubes of both zigzag and...
Topics: Dead loads (Mechanics), Mechanical engineering, Nanomechanics, Nanocomposite, Atomistic model,...
Naval Postgraduate School
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This thesis deals with a simulation of a missile versus target engagement scenario. After driving simplified transfer functions for the missile seeker head, missile autopilot, missile dynamics, and target dynamics, a three dimensional simulation is developed using classical proportional navigation. The scenario is simulated using state variable design. A forward time solution of the two dimensional problem is developed which is converted to an adjoint model. The adjoint model is used to...
Topics: Guided missiles, Transfer functions, Dynamics, Time, Proportional navigation, Antiaircraft...
The cross-flow fan (CFF) is a lifting and propulsion device that retains the advantages of a fixed-wing aircraft by using a ducted lift fan. There is no upper limit to the rotor length-to-diameter ratio of a CFF, allowing the device to be installed along the length of the wing or lifting device. The CFF discharged vector can be easily rotated about the fan axis since the fan has no angular requirements, further allowing the capability of vertical take-off and landing (VTOL) by thrust vectoring....
Topics: cross-flow fan (CFF), vertical take-off and landing (VTOL), straight blades, computational fluid...
Naval Postgraduate School
by Yang, Jia-Horng.
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This dissertation describes the design of an adaptive controller for single-input single-output (SISO) systems with guaranteed bounds on the transient response, and robustness with external disturbances and unmodeled dynamics. Developed from a current approach called \"L1 adaptive controller\", we show that by adding two properly designed low pass filters at the input and at the estimator we can control the transient response and the sensitivity of the overall system to external...
Topics: Electrical engineering., low pass filter, L1 adaptive controller, unmodeled dynamics, non-minimum...
Naval Postgraduate School
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Modeling and control of aerial manipulators are presented in this study. An aerial manipulator is an unmanned aerial vehicle (UAV) equipped with a robotic arm. Aerial manipulators have potential for many applications, such as rescue operations along tall buildings and high cliffs, maintenance and repairing of power line equipment, and retrieval of items from difficult-to-access locations. Control of aerial manipulators is a challenging problem due to dynamic interactions between aerial vehicles...
Topics: unmanned aerial vehicle, multicopter, hexacopter, aerial manipulator, robotic arm, robotic...
The objective of this thesis is to analyze the hydrodynamic properties of a specialized pentahulled, air entrapment, and high-speed planning vessel. Due to the unique features of this hull, a multi-layered approach based on computational fluid dynamics was adopted. The first is a steady state model with no free surface effects. It determines the lift and drag on the hull at a fixed waterline. It does not capture any of the planing effects created by the air entrapment region between hulls nor...
Topics: Fluid dynamics, Data processing, Finite volume method, Hulls (Naval architecture), Design and...
Naval Postgraduate School
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Methods used for designing the ramjet included conic shock tables; isentropic flow tables and the GASTURB code was used for aerothermodynamic performance prediction. The flow field through the proposed geometry was computed using the OVERFLOW code, and small modifications were made. Geometry and solid models were created and built using SolidWorks 3D solid modeling software. A prototype ramjet was manufactured with wind tunnel mounting struts capable of measuring axial force on the model....
Topics: Airplanes, Ramjet engines, Ramjet, GASTURB, OVERFLOW, SolidWorks, Shadowgraph, Computation fluid...
The flow around second-generation controlled-diffusion blades in cascade at stall was examined experimentally through the use of a two-component laser-Doppler velocimeter. Blade surface pressure measurements were also preformed at mid span on the blades at various Reynolds numbers. Flow visualization techniques were used to observe and record the flow on the surface of the blade. A correlation between the experimental results and computational fluid dynamic predictions was attempted in order to...
Topics: Compressors, Blades, Turbomachines, Fluid dynamics, Laser Doppler velocimeter, Controlled...
Naval Postgraduate School
by Samothrakis, Ioannis; Matsuura, Masahiro; Monzon, Carlos Molina; Gil, Benigno; Alcantara, R.
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The objective of this project is to use analysis and modeling techniques of Systems Dynamics to capture the causal relationships of Middle Eastern groups' terrorist activities against the U.S. based on their ideological drivers, as well as the effect of U.S. policies that create dynamics and affect performance and outcomes. The main focus of this analysis is the terrorist groups' human resources. The hypothesis is that Middle Eastern terrorism against the U.S. is affected by the U.S. level of...
Topics: Terrorism|zUnited States|xPrevention., Terrorism aimed at the United States, terrorism dynamics,...
Naval Postgraduate School
by Stein, Teia N.
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This research applies complexity and system dynamics theory to the idea of border security, culminating in the development of a conceptual model that can be used to expand exploration of unconventional leverage points, better understand holistic implications of border policies, and improve sense making for homeland security. How can border security be characterized to better understand what it is, and why are so many divergent opinions being voiced on whether it can be achieved? By...
Topics: Complexity, Borders, Border Security, Globalization, System Dynamics, Sense Making, Systems...
Naval Postgraduate School
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The objective of this thesis is to obtain a better understanding of cloud-top entrainment through an in-depth analysis of entrainment-zone structure. In situ aircraft measurements taken during the Atlantic Stratocumulus Transition Experiment (ASTEX) were used for this purpose. Using data collected from multiple cloud-top penetrations, the presence of an interfacial layer in-between the top of the cloud mixed-layer and the base of the free atmosphere is identified and consequently defined as the...
Topics: Clouds, Dynamics, Boundary layer (Meteorology), Meteorology in aeronautics, Measurement, Cloud-top...
Naval Postgraduate School
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Chaos is a discipline used in understanding complex nonlinear dynamics. The geometric and topological methods of Chaos theory are applied, for the first time, to the study of flight test data. Data analyzed is from the McDonnell Douglas OH-6A Higher Harmonic Control (HHC) test aircraft. HHC is an active control system used to suppress helicopter vibrations. Some of the first practical applications of Chaos methods are demonstrated with the HHC data. Although helicopter vibrations are mostly...
Topics: Aerodynamics, Helicopters, Helicopters,Flight testing, Lyapunov functions., Chaos, Higher Harmonic...
Naval Postgraduate School
by Devoto Gagliardi, Ricardo R.
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Any insurgency is a complex and dynamic phenomenon, as is the process of developing agood strategy to counter it. Understanding such types of dynamic complexity demands that strategists expand the boundaries of their mental models. A good strategy does not rely exclusively on a strategist's talent; it is conditioned on a holistic understanding of causal relationships encompassed in the problem and interactions among variables. This thesis analyzes the Peruvian insurgency of Sendero Luminoso...
Topics: insurgency, Sendero Luminoso, shining path, system dynamics, system dynamic modeling, decision...
Naval Postgraduate School
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Fire departments often respond to incidents at crowded events with no prior planning or coordination with other agencies. The result can be decreased safety for patrons at the events. The purpose of this thesis is to understand causes of injuries at crowded, outside venues and what could make these events safer. This thesis asks how fire department personnel can plan for the safety and care of large crowds at outside venues. The research design includes a review of literature on crowd dynamics...
Topics: root cause analysis, crowded venues, large venues, crowd crush, crowd dynamics, National...
Thorough analysis of drag and power characteristics of hydrodynamic power turbines is necessary for the efficient extraction of energy available at sea. In an effort to obtain these characteristics for a three-bladed, axial-flow hydroturbine, used to provide electric power on small sailing vessels, a load cell and voltage measuring system was installed on a carriage in a towing tank for analysis across a speed range of 0.5 to 1.8 m/s. A high-speed camera was used to determine the precise...
Topics: Hydropower Turbine, Hydrodynamic Power Generations, Experimental Towing Tank Analysis of...
Naval Postgraduate School
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The thesis proposes a real-time control algorithm for the cooperation of a joint team consisting of a Quadrotor and a Ground robot for coordinated ISR missions. The intended application focuses on indoor environments, where Global Positioning System signals are unreliable or simply unavailable so that the control algorithms must rely on local sensor information. The thesis describes the appropriate set up of the lab and includes simulations using a full dynamic model of the quadrotor and robot,...
Topics: Cameras., Quadrotor, Ground Robot, Cooperation, Localization System, Quanser, Optitrack cameras,...